In my scene I have positioned the grid as I want it, now I would like to use the X, Y and Z coordinates from my grid as the coordinate system.  
 
In the tutorials I have read it looks like the only ways to setup and valid coordinate system is by specifying tracked points for the various properties, but I would just like the coordinate system to sit there as it does when I create it after adjusting my grid.  Is there a way to make a coordinate system valid by using the grid?

Hi,
 
In fact, what you did is sufficient.
When you move the grid, your entire scene is translated/rotated/scale.
The world origin remains the center of the grid, so all your 3D points and camera have their coordinates corresponding to your new grid position.
Moving the grid is a simple way to define a coordinate system.
 
Hope it helps...
 
PS:
If the grid is where you want it to be, don't define a coordinate system with the "coordinate system tool". If you already did, delete it.

Hi, thanks for the reply.  Yeah, I'm have just been letting the grid sit there and it has been working fine but I was also hoping to put in some "point relations" so that I can get them to match the actual set a little more closely and it doesn't seem as though MM will let me do that without a coordinate system.  Is there a way to use point relationships without a coordinate system?